Latex modified concrete (LMC) is often used to overlay a bridge deck or parking deck. LMC requires special techniques and special care. For a good job, five steps must be followed. All five steps are crucial. They must be done quickly, in sequence, without lags.

PREPARE THE SURFACE THOROUGHLY

You must remove the top 1/4 inch of concrete and any weak concrete below the surface. Use hydrodemolition or scarifying equipment to remove the top surface and power-driven hand tools to remove the deteriorated concrete underneath.

MAKE THE LMC ONSITE IN A MOBILE BATCHER MIXER

Because LMC should not be mixed for more than 5 minutes, you must make it onsite. You can use a drum mixer or a continuous mobile batcher mixer.

USE A SELF-PROPELLED FINISHING MACHINE

For small areas or parking decks obstructed by columns, you can place LMC with a screed and spud vibrators. For bridge deck overlays, use a self-propelled finishing machine that can move forward and backward. Vibrating screeds have been used, but roller finishing machines are now more common.

PLACE AND FINISH THE CONCRETE QUICKLY

You normally have only about 10 minutes to screed and finish LMC after depositing it on the deck. This means you need several workers who must work fast.

WET CURE FOR 24 HOURS, THEN DRY CURE FOR 72 HOURS

LMC forms a plastic film at the surface upon drying, usually within 25 minutes in hot, dry weather. To prevent the surface from cracking because of this, you must cover it with presaturated burlap as soon as it will support the burlap without significant deformation. After 24 hours, remove the burlap and allow the LMC to dry cure for 72 hours before opening the deck to traffic.